Add a target edit form and reachable header/timeout fields (closes #127)

A target's configuration was write-once: `internal/server/routes.go`
registered create, toggle and delete for targets but no edit route, so
correcting a typo in a destination meant deleting the target and
recreating it. Masking the stored value made that unrecoverable from
the UI.

Headers and timeout were worse than write-once. `HTTPTargetConfig` has
carried `Headers` and `Timeout` and the delivery path has honoured both,
but `buildURLTargetConfig` only ever wrote `{"url":...}` and no form
offered either field, so a destination needing an `Authorization` header
could not be configured through the UI at all.

Both paths now build their configuration through `buildTargetConfig`, so
an edited destination is SSRF-validated exactly as a new one is. The
destination check lives in one helper that both reach, leaving the guard's
entry point untouched.

The edit form pre-fills the stored destination and header values in full.
That is the one intentional exception to the masking rule, narrowed by
the route it lives on: `RequireAuth`, `NoCache`, and the webhook's
ownership check. `delivery.TargetView` is unchanged, so every other page
still masks.

A target's type stays fixed at creation: each type stores a different
configuration shape and its delivery history is recorded against the row,
so changing it is really a different target.

Header and timeout input that could not be delivered as written is
rejected rather than stored: a malformed line, an invalid name, a control
character in a value, a repeated name, a header the delivery engine
overwrites regardless, or a timeout that is not a whole number of seconds
within the ceiling. Storing input that provably never reaches the wire
would report a configuration that did not take effect.

internal/handlers/export_test.go

@@ -69,18 +69,29 @@ func (s *Handlers) RenderTemplateForTest(
 	s.renderTemplate(w, r, pageTemplate, data)
 }
 
-// BuildSlackTargetConfigForTest exposes buildURLTargetConfig
-// with the Slack target parameters for use in the
-// handlers_test package.
+// BuildSlackTargetConfigForTest exposes
+// buildSlackTargetConfig for use in the handlers_test package.
 func (s *Handlers) BuildSlackTargetConfigForTest(
 	w http.ResponseWriter,
 	r *http.Request,
 	targetURL string,
 ) (string, error) {
-	return s.buildURLTargetConfig(
-		w, r, targetURL, "webhookUrl",
-		"Webhook URL is required for Slack targets",
-	)
+	return s.buildSlackTargetConfig(w, r, targetURL)
+}
+
+// BuildHTTPTargetConfigForTest exposes buildHTTPTargetConfig
+// for use in the handlers_test package, taking the form fields
+// an HTTP target's configuration is built from.
+func (s *Handlers) BuildHTTPTargetConfigForTest(
+	w http.ResponseWriter,
+	r *http.Request,
+	targetURL, headers, timeout string,
+) (string, error) {
+	return s.buildHTTPTargetConfig(w, r, targetFormInput{
+		URL:     targetURL,
+		Headers: headers,
+		Timeout: timeout,
+	})
 }
 
 // BuildDatabaseTargetConfigForTest exposes

internal/handlers/handlers.go

@@ -124,6 +124,7 @@ func New(
 		"source_detail.html": parsePageTemplate("source_detail.html"),
 		"source_edit.html":   parsePageTemplate("source_edit.html"),
 		"source_logs.html":   parsePageTemplate("source_logs.html"),
+		"target_edit.html":   parsePageTemplate("target_edit.html"),
 	}
 
 	lc.Append(fx.Hook{

internal/handlers/source_management.go

@@ -1029,9 +1029,7 @@ func (h *Handlers) processTargetCreate(
 	// Referer headers and error trackers record.
 	name := r.PostFormValue("name")
 	targetType := database.TargetType(r.PostFormValue("type"))
-	targetURL := r.PostFormValue("url")
 	maxRetriesStr := r.PostFormValue("max_retries")
-	expiry := r.PostFormValue("expiry")
 
 	if name == "" {
 		http.Error(
@@ -1051,7 +1049,7 @@ func (h *Handlers) processTargetCreate(
 	}
 
 	configJSON, err := h.buildTargetConfig(
-		w, r, targetType, targetURL, expiry,
+		w, r, targetType, targetFormInputFrom(r),
 	)
 	if err != nil {
 		return
@@ -1108,28 +1106,60 @@ func parseNonNegativeInt(s string) int {
 	return 0
 }
 
-// buildTargetConfig builds the JSON config string for a target.
-// The expiry form value is read by the caller (which bounds the
-// request body) and applies to database targets only.
+// targetFormInput carries the raw form values describing a target's
+// configuration. Both the create and the edit path fill one and hand
+// it to buildTargetConfig, so neither can come to validate a
+// destination differently from the other.
+type targetFormInput struct {
+	// URL is the destination for an HTTP target and the webhook URL
+	// for a Slack target.
+	URL string
+	// Headers is an HTTP target's headers, one "Name: value" per
+	// line.
+	Headers string
+	// Timeout is an HTTP target's per-request timeout in seconds.
+	Timeout string
+	// Expiry is a database (archive) target's row expiry.
+	Expiry string
+}
+
+// targetFormInputFrom reads the configuration fields from a request
+// body. The body size cap is enforced by the MaxBodySize middleware,
+// which runs before CSRF parses the form.
+//
+// Every field is read with PostFormValue, not FormValue. FormValue
+// falls back to the query string, which would let
+// `POST /source/{id}/targets?url=https://hooks.slack.com/...`
+// configure a target from a value the request line carries — and the
+// request line, unlike the body, is what logs, proxies, Referer
+// headers and error trackers record. The headers field is under the
+// same rule and for the same reason: its values are authorization
+// tokens.
+func targetFormInputFrom(r *http.Request) targetFormInput {
+	return targetFormInput{
+		URL:     r.PostFormValue("url"),
+		Headers: r.PostFormValue("headers"),
+		Timeout: r.PostFormValue("timeout"),
+		Expiry:  r.PostFormValue("expiry"),
+	}
+}
+
+// buildTargetConfig builds the JSON config string for a target from
+// the submitted form values, writing its own 4xx response on
+// rejection. Which fields of in apply depends on the target type.
 func (h *Handlers) buildTargetConfig(
 	w http.ResponseWriter,
 	r *http.Request,
 	targetType database.TargetType,
-	targetURL, expiry string,
+	in targetFormInput,
 ) (string, error) {
 	switch targetType {
 	case database.TargetTypeHTTP:
-		return h.buildURLTargetConfig(
-			w, r, targetURL, "url",
-			"URL is required for HTTP targets",
-		)
+		return h.buildHTTPTargetConfig(w, r, in)
 	case database.TargetTypeSlack:
-		return h.buildURLTargetConfig(
-			w, r, targetURL, "webhookUrl",
-			"Webhook URL is required for Slack targets",
-		)
+		return h.buildSlackTargetConfig(w, r, in.URL)
 	case database.TargetTypeDatabase:
-		return h.buildDatabaseTargetConfig(w, expiry)
+		return h.buildDatabaseTargetConfig(w, in.Expiry)
 	case database.TargetTypeLog:
 		return "", nil
 	default:
@@ -1142,14 +1172,83 @@ func (h *Handlers) buildTargetConfig(
 	}
 }
 
-// buildURLTargetConfig builds config JSON for a target whose
-// configuration is a single SSRF-validated URL stored under
-// configKey. missingMsg is the error shown when no URL is given.
-func (h *Handlers) buildURLTargetConfig(
+// buildHTTPTargetConfig builds config JSON for an HTTP target: an
+// SSRF-validated destination plus the optional headers and timeout
+// the delivery path honours.
+func (h *Handlers) buildHTTPTargetConfig(
 	w http.ResponseWriter,
 	r *http.Request,
-	targetURL, configKey, missingMsg string,
+	in targetFormInput,
 ) (string, error) {
+	err := h.validateTargetURL(
+		w, r, in.URL, "URL is required for HTTP targets",
+	)
+	if err != nil {
+		return "", err
+	}
+
+	headers, err := delivery.ParseTargetHeaders(in.Headers)
+	if err != nil {
+		http.Error(
+			w,
+			"Invalid headers: "+err.Error(),
+			http.StatusBadRequest,
+		)
+
+		return "", err
+	}
+
+	timeout, err := delivery.ParseTargetTimeout(in.Timeout)
+	if err != nil {
+		http.Error(
+			w,
+			"Invalid timeout: "+err.Error(),
+			http.StatusBadRequest,
+		)
+
+		return "", err
+	}
+
+	return marshalTargetConfig(w, delivery.HTTPTargetConfig{
+		URL:     in.URL,
+		Headers: headers,
+		Timeout: timeout,
+	})
+}
+
+// buildSlackTargetConfig builds config JSON for a Slack target,
+// whose whole configuration is one SSRF-validated webhook URL.
+func (h *Handlers) buildSlackTargetConfig(
+	w http.ResponseWriter,
+	r *http.Request,
+	targetURL string,
+) (string, error) {
+	err := h.validateTargetURL(
+		w, r, targetURL,
+		"Webhook URL is required for Slack targets",
+	)
+	if err != nil {
+		return "", err
+	}
+
+	return marshalTargetConfig(w, delivery.SlackTargetConfig{
+		WebhookURL: targetURL,
+	})
+}
+
+// validateTargetURL rejects an empty or SSRF-blocked destination,
+// writing the 400 itself. missingMsg is the error shown when no URL
+// is given.
+//
+// It is the single point at which a user-supplied destination enters
+// the SSRF guard, on create and on edit alike. An edit path that
+// reached storage without passing through here would reopen the hole
+// the guard closes.
+func (h *Handlers) validateTargetURL(
+	w http.ResponseWriter,
+	r *http.Request,
+	targetURL, missingMsg string,
+) error {
 	if targetURL == "" {
 		http.Error(
 			w,
@@ -1157,7 +1256,7 @@ func (h *Handlers) buildURLTargetConfig(
 			http.StatusBadRequest,
 		)
 
-		return "", errMissingURL
+		return errMissingURL
 	}
 
 	err := delivery.ValidateTargetURL(
@@ -1178,11 +1277,18 @@ func (h *Handlers) buildURLTargetConfig(
 			http.StatusBadRequest,
 		)
 
-		return "", err
+		return err
 	}
 
-	cfg := map[string]any{configKey: targetURL}
+	return nil
+}
 
+// marshalTargetConfig serialises a target configuration for storage,
+// writing a 500 itself if it cannot.
+func marshalTargetConfig(
+	w http.ResponseWriter,
+	cfg any,
+) (string, error) {
 	configBytes, err := json.Marshal(cfg)
 	if err != nil {
 		http.Error(
@@ -1222,19 +1328,9 @@ func (h *Handlers) buildDatabaseTargetConfig(
 		return "", err
 	}
 
-	cfg := map[string]any{"expiry": expiry}
-
-	configBytes, err := json.Marshal(cfg)
-	if err != nil {
-		http.Error(
-			w, "Internal server error",
-			http.StatusInternalServerError,
-		)
-
-		return "", err
-	}
-
-	return string(configBytes), nil
+	return marshalTargetConfig(
+		w, map[string]any{"expiry": expiry},
+	)
 }
 
 // HandleEntrypointDelete handles deleting an entrypoint.

internal/handlers/target_edit.go

@@ -0,0 +1,221 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/go-chi/chi"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+)
+
+// targetEditTemplate is the page the target edit form renders.
+const targetEditTemplate = "target_edit.html"
+
+// tmplKeyTarget is the template data key for the target being
+// edited, and tmplKeyMaxTimeout for the timeout ceiling the form
+// tells the user about.
+const (
+	tmplKeyTarget     = "Target"
+	tmplKeyMaxTimeout = "MaxTimeout"
+)
+
+// configUnreadableMessage is shown when a target's stored
+// configuration does not parse. It says plainly that saving replaces
+// the stored value rather than preserving it, because the form
+// cannot pre-fill what it could not read.
+const configUnreadableMessage = "The stored configuration for this " +
+	"target could not be read. Enter the values below; saving " +
+	"replaces the stored configuration."
+
+// targetEditView is the display model for the target edit page.
+//
+// It carries the target's row fields alongside its UNMASKED
+// configuration, and deliberately omits database.Target's raw
+// Config blob: the form renders named fields, and giving the
+// template the blob as well would put an unreviewed second path to
+// the credential on the page.
+type targetEditView struct {
+	ID         string
+	Name       string
+	Type       database.TargetType
+	Active     bool
+	MaxRetries int
+	Config     delivery.TargetConfigForm
+}
+
+// HandleTargetEdit shows the form to edit a target.
+//
+// This page is the one place the full destination URL and header
+// values are shown. It is reachable only through the
+// /source/{sourceID} route group, which supplies RequireAuth and
+// NoCache, and only for a target of a webhook the session's user
+// owns; masking (delivery.TargetView) is unchanged everywhere else.
+func (h *Handlers) HandleTargetEdit() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		webhook, target, ok := h.ownedTarget(w, r)
+		if !ok {
+			return
+		}
+
+		cfg, err := delivery.NewTargetConfigForm(target)
+		msg := ""
+
+		if err != nil {
+			// The error carries the parse failure, never the
+			// blob, so it is safe to log against the target id.
+			h.log.Warn(
+				"stored target config could not be read for editing",
+				"target_id", target.ID,
+				"error", err,
+			)
+
+			msg = configUnreadableMessage
+		}
+
+		h.renderTargetEdit(w, r, webhook, target, cfg, msg)
+	}
+}
+
+// HandleTargetEditSubmit handles the target edit form submission.
+func (h *Handlers) HandleTargetEditSubmit() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		webhook, target, ok := h.ownedTarget(w, r)
+		if !ok {
+			return
+		}
+
+		// The body size cap is enforced by the MaxBodySize
+		// middleware, which runs before CSRF parses the form.
+		err := r.ParseForm()
+		if err != nil {
+			http.Error(
+				w, "Bad request", http.StatusBadRequest,
+			)
+
+			return
+		}
+
+		h.applyTargetEdit(w, r, webhook, target)
+	}
+}
+
+// applyTargetEdit validates and saves target edits.
+//
+// The submitted configuration goes through buildTargetConfig, the
+// same builder the create path uses, so an edited destination is
+// SSRF-validated exactly as a new one is.
+//
+// The target's type is not editable. Each type stores a different
+// configuration shape and its delivery history is recorded against
+// the target row, so changing the type of an existing target is
+// really the creation of a different one. The stored type decides
+// which fields the form offers and which builder runs.
+func (h *Handlers) applyTargetEdit(
+	w http.ResponseWriter,
+	r *http.Request,
+	webhook database.Webhook,
+	target *database.Target,
+) {
+	name := r.PostFormValue("name")
+	if name == "" {
+		http.Error(
+			w, "Name is required", http.StatusBadRequest,
+		)
+
+		return
+	}
+
+	configJSON, err := h.buildTargetConfig(
+		w, r, target.Type, targetFormInputFrom(r),
+	)
+	if err != nil {
+		// buildTargetConfig has already written the response.
+		return
+	}
+
+	target.Name = name
+	target.Config = configJSON
+
+	// Retries are offered only by the forms for target types that
+	// retry, so an absent field means "this form does not edit
+	// retries" rather than "set them to zero". Reading it
+	// unconditionally would silently disable retries on any target
+	// saved from a form that does not render the input.
+	if r.PostForm.Has("max_retries") {
+		target.MaxRetries = parseNonNegativeInt(
+			r.PostFormValue("max_retries"),
+		)
+	}
+
+	err = h.db.DB().Save(target).Error
+	if err != nil {
+		h.serverError(w, "failed to update target", err)
+
+		return
+	}
+
+	http.Redirect(
+		w, r, "/source/"+webhook.ID, http.StatusSeeOther,
+	)
+}
+
+// renderTargetEdit renders the target edit page with an optional
+// error message.
+func (h *Handlers) renderTargetEdit(
+	w http.ResponseWriter,
+	r *http.Request,
+	webhook database.Webhook,
+	target *database.Target,
+	cfg delivery.TargetConfigForm,
+	errMsg string,
+) {
+	// The template calls Webhook methods, which take pointer
+	// receivers; html/template cannot address a value stored in a
+	// map.
+	data := map[string]any{
+		tmplKeyWebhook: &webhook,
+		tmplKeyTarget: targetEditView{
+			ID:         target.ID,
+			Name:       target.Name,
+			Type:       target.Type,
+			Active:     target.Active,
+			MaxRetries: target.MaxRetries,
+			Config:     cfg,
+		},
+		tmplKeyMaxTimeout: delivery.MaxTargetTimeoutSeconds,
+		tmplKeyError:      errMsg,
+	}
+
+	h.renderTemplate(w, r, targetEditTemplate, data)
+}
+
+// ownedTarget resolves the request's sourceID and targetID
+// parameters to a target of a webhook the session's user owns.
+//
+// Ownership is decided by the webhook, and the target is then
+// scoped to that webhook, so a target id belonging to someone
+// else's webhook is a 404 rather than an edit of their target. It
+// reports false once it has written the response.
+func (h *Handlers) ownedTarget(
+	w http.ResponseWriter,
+	r *http.Request,
+) (database.Webhook, *database.Target, bool) {
+	webhook, ok := h.ownedWebhook(w, r)
+	if !ok {
+		return database.Webhook{}, nil, false
+	}
+
+	var target database.Target
+
+	err := h.db.DB().Where(
+		"id = ? AND webhook_id = ?",
+		chi.URLParam(r, "targetID"), webhook.ID,
+	).First(&target).Error
+	if err != nil {
+		http.NotFound(w, r)
+
+		return database.Webhook{}, nil, false
+	}
+
+	return webhook, &target, true
+}

internal/handlers/target_edit_test.go

@@ -0,0 +1,637 @@
+package handlers_test
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+
+	"github.com/go-chi/chi"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm/clause"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+)
+
+// The destinations the target edit tests configure. Both are literal
+// public addresses rather than hostnames so the SSRF check resolves
+// nothing: with a hostname, a sandbox without DNS would reject the
+// URL for the wrong reason and a test asserting rejection would pass
+// even with the guard removed.
+const (
+	editOriginalURL = "https://93.184.216.34/hooks/original"
+	editReplacedURL = "https://93.184.216.34/hooks/replaced"
+	// editBlockedURL resolves to loopback, which the SSRF guard
+	// refuses. It is what proves the guard runs on the edit path.
+	editBlockedURL = "http://127.0.0.1/hooks/internal"
+)
+
+// editAuthHeader carries a bearer credential, the case the headers
+// field exists for.
+const (
+	editBearerSecret = "QQEDITSECRETQQ"
+	editAuthHeader   = "Authorization: Bearer " + editBearerSecret
+)
+
+// targetRouter mounts the target create and edit routes on a chi
+// router so the handlers see the URL parameters they read.
+func targetRouter(env *sourceTestEnv) *chi.Mux {
+	router := chi.NewRouter()
+	router.Post(
+		"/source/{sourceID}/targets",
+		env.handlers.HandleTargetCreate(),
+	)
+	router.Get(
+		"/source/{sourceID}/targets/{targetID}/edit",
+		env.handlers.HandleTargetEdit(),
+	)
+	router.Post(
+		"/source/{sourceID}/targets/{targetID}/edit",
+		env.handlers.HandleTargetEditSubmit(),
+	)
+
+	return router
+}
+
+// serveTarget drives one request through the target routes as the
+// authenticated test user.
+func serveTarget(
+	env *sourceTestEnv,
+	method, path string,
+	form url.Values,
+) *httptest.ResponseRecorder {
+	body := ""
+	if form != nil {
+		body = form.Encode()
+	}
+
+	req := httptest.NewRequestWithContext(
+		context.Background(), method, path,
+		strings.NewReader(body),
+	)
+	if form != nil {
+		req.Header.Set(
+			"Content-Type",
+			"application/x-www-form-urlencoded",
+		)
+	}
+
+	for _, c := range env.cookies {
+		req.AddCookie(c)
+	}
+
+	w := httptest.NewRecorder()
+	targetRouter(env).ServeHTTP(w, req)
+
+	return w
+}
+
+// seedHTTPTarget creates a webhook and an HTTP target on it through
+// the real create handler, so every case starts from a target the
+// production path produced rather than a hand-written row.
+//
+// Standing the fx app up is what a handler test mostly costs, and
+// internal/handlers is already the slowest package in the suite, so
+// the tests below share one env per test function and give each case
+// its own webhook rather than its own app.
+func seedHTTPTarget(
+	t *testing.T,
+	env *sourceTestEnv,
+	headers, timeout string,
+) (database.Webhook, database.Target) {
+	t.Helper()
+
+	webhook := seedWebhookWithRetention(t, env.db, 30)
+
+	form := url.Values{}
+	form.Set("name", "original-name")
+	form.Set("type", string(database.TargetTypeHTTP))
+	form.Set("url", editOriginalURL)
+	form.Set("headers", headers)
+	form.Set("timeout", timeout)
+	form.Set("max_retries", "3")
+
+	w := serveTarget(
+		env, http.MethodPost,
+		"/source/"+webhook.ID+"/targets", form,
+	)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	targets := targetsForWebhook(t, env.db, webhook.ID)
+	require.Len(t, targets, 1)
+
+	return webhook, targets[0]
+}
+
+// storedTarget reloads a target row.
+func storedTarget(
+	t *testing.T,
+	env *sourceTestEnv,
+	targetID string,
+) database.Target {
+	t.Helper()
+
+	var target database.Target
+
+	require.NoError(
+		t,
+		env.db.DB().Where("id = ?", targetID).
+			First(&target).Error,
+	)
+
+	return target
+}
+
+// storedHTTPConfig reloads a target and parses its stored HTTP
+// configuration.
+func storedHTTPConfig(
+	t *testing.T,
+	env *sourceTestEnv,
+	targetID string,
+) delivery.HTTPTargetConfig {
+	t.Helper()
+
+	var cfg delivery.HTTPTargetConfig
+
+	require.NoError(
+		t,
+		json.Unmarshal(
+			[]byte(storedTarget(t, env, targetID).Config), &cfg,
+		),
+	)
+
+	return cfg
+}
+
+// editForm is the fully populated edit submission for an HTTP
+// target.
+func editForm(targetURL, headers, timeout string) url.Values {
+	form := url.Values{}
+	form.Set("name", "edited-name")
+	form.Set("url", targetURL)
+	form.Set("headers", headers)
+	form.Set("timeout", timeout)
+	form.Set("max_retries", "5")
+
+	return form
+}
+
+// submitTargetEdit posts the edit form for a target.
+func submitTargetEdit(
+	env *sourceTestEnv,
+	webhookID, targetID string,
+	form url.Values,
+) *httptest.ResponseRecorder {
+	return serveTarget(
+		env, http.MethodPost,
+		"/source/"+webhookID+"/targets/"+targetID+"/edit",
+		form,
+	)
+}
+
+// TestHandleTargetCreate_Configuration covers the half of the gap
+// that is not about editing at all: HTTPTargetConfig has carried
+// Headers and Timeout, and the delivery path has honoured them, but
+// the create form wrote {"url":...} and nothing else, so a
+// destination needing an Authorization header could not be
+// configured through the UI at all.
+func TestHandleTargetCreate_Configuration(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	t.Run("stores headers and timeout", func(t *testing.T) {
+		t.Parallel()
+		assertCreateStoresHeadersAndTimeout(t, env)
+	})
+
+	t.Run("without them keeps a url-only config", func(t *testing.T) {
+		t.Parallel()
+		assertCreateKeepsURLOnlyConfig(t, env)
+	})
+}
+
+func assertCreateStoresHeadersAndTimeout(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	_, target := seedHTTPTarget(
+		t, env, editAuthHeader+"\nX-Tenant: acme\n", "12",
+	)
+
+	cfg := storedHTTPConfig(t, env, target.ID)
+
+	assert.Equal(t, editOriginalURL, cfg.URL)
+	assert.Equal(t, 12, cfg.Timeout)
+	assert.Equal(
+		t,
+		map[string]string{
+			"Authorization": "Bearer " + editBearerSecret,
+			"X-Tenant":      "acme",
+		},
+		cfg.Headers,
+	)
+}
+
+// Without the new fields the stored shape must be the same
+// {"url":...} the create form wrote before they existed, so no
+// existing target's configuration is rewritten by this change.
+func assertCreateKeepsURLOnlyConfig(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	_, target := seedHTTPTarget(t, env, "", "")
+
+	assert.JSONEq(
+		t, `{"url":"`+editOriginalURL+`"}`, target.Config,
+	)
+}
+
+// TestHandleTargetEditSubmit_Saves is the round trip the issue asks
+// for: create a target, edit it, and confirm the stored config
+// changed.
+func TestHandleTargetEditSubmit_Saves(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	t.Run("changes the destination URL", func(t *testing.T) {
+		t.Parallel()
+		assertEditChangesDestination(t, env)
+	})
+
+	t.Run("round trips headers and timeout", func(t *testing.T) {
+		t.Parallel()
+		assertEditRoundTripsHeadersAndTimeout(t, env)
+	})
+
+	t.Run("clearing them removes them", func(t *testing.T) {
+		t.Parallel()
+		assertEditClearingRemovesThem(t, env)
+	})
+
+	t.Run("absent max_retries is not zeroed", func(t *testing.T) {
+		t.Parallel()
+		assertEditKeepsAbsentMaxRetries(t, env)
+	})
+}
+
+func assertEditChangesDestination(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editReplacedURL, "", ""),
+	)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	assert.Equal(
+		t,
+		editReplacedURL,
+		storedHTTPConfig(t, env, target.ID).URL,
+	)
+
+	reloaded := storedTarget(t, env, target.ID)
+	assert.Equal(t, "edited-name", reloaded.Name)
+	assert.Equal(t, 5, reloaded.MaxRetries)
+	assert.Equal(
+		t, database.TargetTypeHTTP, reloaded.Type,
+		"the edit form must not change a target's type",
+	)
+}
+
+// The two previously unreachable fields must survive create,
+// pre-fill and save.
+func assertEditRoundTripsHeadersAndTimeout(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, editAuthHeader, "7")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(
+			editOriginalURL,
+			"Authorization: Bearer rotated\nX-Trace: on",
+			"21",
+		),
+	)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	cfg := storedHTTPConfig(t, env, target.ID)
+
+	assert.Equal(t, 21, cfg.Timeout)
+	assert.Equal(
+		t,
+		map[string]string{
+			"Authorization": "Bearer rotated",
+			"X-Trace":       "on",
+		},
+		cfg.Headers,
+	)
+}
+
+// The direction a naive "only set what was submitted" implementation
+// gets wrong: an emptied field must remove the stored value, not
+// leave the previous one in place.
+func assertEditClearingRemovesThem(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, editAuthHeader, "7")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editOriginalURL, "", ""),
+	)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	cfg := storedHTTPConfig(t, env, target.ID)
+
+	assert.Empty(t, cfg.Headers)
+	assert.Zero(t, cfg.Timeout)
+}
+
+// Retries are offered only by the forms for target types that retry.
+// An absent field means the form does not edit retries, not that
+// they should be turned off.
+func assertEditKeepsAbsentMaxRetries(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+	require.Equal(t, 3, target.MaxRetries)
+
+	form := editForm(editOriginalURL, "", "")
+	form.Del("max_retries")
+
+	w := submitTargetEdit(env, webhook.ID, target.ID, form)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	assert.Equal(
+		t, 3, storedTarget(t, env, target.ID).MaxRetries,
+	)
+}
+
+// TestHandleTargetEdit_PrefillsTheStoredValuesUnmasked covers the
+// deliberate exception to the masking rule. The operator cannot
+// correct a value they cannot see, so this page — and only this page
+// — renders the destination and the header values in full.
+func TestHandleTargetEdit_PrefillsTheStoredValuesUnmasked(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	webhook, target := seedHTTPTarget(t, env, editAuthHeader, "7")
+
+	w := serveTarget(
+		env, http.MethodGet,
+		"/source/"+webhook.ID+"/targets/"+target.ID+"/edit",
+		nil,
+	)
+	require.Equal(t, http.StatusOK, w.Code)
+
+	page := w.Body.String()
+
+	assert.Contains(t, page, editOriginalURL)
+	assert.Contains(t, page, "Bearer "+editBearerSecret)
+	assert.Contains(t, page, `value="7"`)
+	assert.Contains(t, page, "original-name")
+}
+
+// TestHandleTargetEditSubmit_Rejects covers every submission that
+// must not reach storage.
+//
+// The SSRF case is the most important assertion on this change: the
+// edited destination goes through the same guard the create path
+// uses. An edit that stored an unvalidated URL would reopen a closed
+// hole, since a target could then be created public and edited to
+// point at loopback.
+//
+// The header and timeout cases keep input that could not be
+// delivered as written out of storage: a stored value that provably
+// never reaches the wire reports a configuration that did not take
+// effect.
+func TestHandleTargetEditSubmit_Rejects(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	t.Run("an SSRF-blocked destination", func(t *testing.T) {
+		t.Parallel()
+		assertEditRejectsBlockedDestination(t, env)
+	})
+
+	t.Run("a query-string destination", func(t *testing.T) {
+		t.Parallel()
+		assertEditIgnoresQueryString(t, env)
+	})
+
+	headerCases := map[string]string{
+		"no colon":        "Authorization Bearer token",
+		"empty name":      ": value",
+		"invalid name":    "X Bad Name: value",
+		"reserved header": "User-Agent: curl/8",
+		"duplicate name":  "X-A: one\nx-a: two",
+	}
+
+	for name, headers := range headerCases {
+		t.Run("headers: "+name, func(t *testing.T) {
+			t.Parallel()
+			assertEditRejectsHeaders(t, env, headers)
+		})
+	}
+
+	timeoutCases := map[string]string{
+		"not a number": "soon",
+		"negative":     "-1",
+		"over ceiling": "100000",
+	}
+
+	for name, timeout := range timeoutCases {
+		t.Run("timeout: "+name, func(t *testing.T) {
+			t.Parallel()
+			assertEditRejectsTimeout(t, env, timeout)
+		})
+	}
+}
+
+func assertEditRejectsBlockedDestination(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editBlockedURL, "", ""),
+	)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+	assert.Contains(t, w.Body.String(), "Invalid target URL")
+	assert.Equal(
+		t, editOriginalURL,
+		storedHTTPConfig(t, env, target.ID).URL,
+		"a rejected edit must leave the stored config alone",
+	)
+}
+
+// The ingress rule the create path already follows applies to the
+// edit path too: reading a field with FormValue would let the request
+// line carry the credential, and the request line is what logs,
+// proxies and Referer headers record.
+func assertEditIgnoresQueryString(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+
+	form := url.Values{}
+	form.Set("name", "edited-name")
+
+	w := serveTarget(
+		env, http.MethodPost,
+		"/source/"+webhook.ID+"/targets/"+target.ID+
+			"/edit?url="+url.QueryEscape(editReplacedURL)+
+			"&headers="+url.QueryEscape(editAuthHeader),
+		form,
+	)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+
+	cfg := storedHTTPConfig(t, env, target.ID)
+	assert.Equal(t, editOriginalURL, cfg.URL)
+	assert.Empty(t, cfg.Headers)
+}
+
+func assertEditRejectsHeaders(
+	t *testing.T, env *sourceTestEnv, headers string,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editOriginalURL, headers, ""),
+	)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+	assert.Contains(t, w.Body.String(), "Invalid headers")
+	assert.Empty(
+		t, storedHTTPConfig(t, env, target.ID).Headers,
+		"a rejected header must not be stored",
+	)
+}
+
+func assertEditRejectsTimeout(
+	t *testing.T, env *sourceTestEnv, timeout string,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "9")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editOriginalURL, "", timeout),
+	)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+	assert.Contains(t, w.Body.String(), "Invalid timeout")
+	assert.Equal(
+		t, 9, storedHTTPConfig(t, env, target.ID).Timeout,
+		"a rejected timeout must leave the stored one alone",
+	)
+}
+
+// TestHandleTargetEdit_Scoping keeps the edit routes scoped the way
+// the delete and toggle routes are: ownership is decided by the
+// webhook, and the target is then scoped to it.
+func TestHandleTargetEdit_Scoping(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	t.Run("a target of another webhook", func(t *testing.T) {
+		t.Parallel()
+		assertTargetOfAnotherWebhook404s(t, env)
+	})
+
+	t.Run("a webhook of another user", func(t *testing.T) {
+		t.Parallel()
+		assertWebhookOfAnotherUser404s(t, env)
+	})
+}
+
+// A target id from elsewhere must not become editable by pairing it
+// with a webhook the user does own.
+func assertTargetOfAnotherWebhook404s(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	mine := seedWebhookWithRetention(t, env.db, 30)
+	_, target := seedHTTPTarget(t, env, "", "")
+
+	get := serveTarget(
+		env, http.MethodGet,
+		"/source/"+mine.ID+"/targets/"+target.ID+"/edit", nil,
+	)
+	assert.Equal(t, http.StatusNotFound, get.Code)
+
+	post := submitTargetEdit(
+		env, mine.ID, target.ID,
+		editForm(editReplacedURL, "", ""),
+	)
+	assert.Equal(t, http.StatusNotFound, post.Code)
+
+	assert.Equal(
+		t, editOriginalURL,
+		storedHTTPConfig(t, env, target.ID).URL,
+	)
+}
+
+func assertWebhookOfAnotherUser404s(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	other := &database.Webhook{
+		UserID:        "some-other-user",
+		Name:          "not mine",
+		RetentionDays: 30,
+	}
+	require.NoError(
+		t,
+		env.db.DB().Omit(clause.Associations).Create(other).Error,
+	)
+
+	target := seedConfiguredTarget(
+		t, env.db, other.ID, database.TargetTypeHTTP,
+		`{"url":"`+editOriginalURL+`"}`,
+	)
+
+	w := serveTarget(
+		env, http.MethodGet,
+		"/source/"+other.ID+"/targets/"+target.ID+"/edit", nil,
+	)
+
+	assert.Equal(t, http.StatusNotFound, w.Code)
+}